1. Field of the Invention
This invention relates to a method for testing metals. More particularly, the invention relates to a method of determining the amount of gold or other precious metal in an alloy and reporting it. In gold samples, the gold content is reported as "karatage".
2. Description of the Prior Art
Metal alloys are homogeneous in content and it is generally considered virtually impossible to determine the content of any specific metal in an alloy by visual observation. Historically, the content of a specific metal in an alloy of metals is determined by qualitative and quantitative chemical analysis occurring in a laboratory which requires grinding the metal to obtain a sample, solubilizing the sample with acid and titrating the solution against a known standard; all resulting in partial loss of the metal.
Beginning in late 1979, electricity was combined with chemical electrolytes in a small device to determine the presence or absence of certain metals in an alloy composition. U.S. Pat. No. 4,179,349 concerns the use of a probe containing an electrolyte that is placed in electrical contact with a test piece of metal alloy to determine through voltage-current profiles the presence or absence of chromium in stainless steels that had been subjected to extended heat such as to become "sensitized". This device measured only the presence or absence of chromium and not any quantitative amounts thereof.
Later, U.S. Pat. No. 4,240,892 discloses a similar device using chemical electrolytes placed in physical and electrical contact with a metal alloy test specimen to determine the relative anodic properties of metals that had been subjected to shaping or bending to determine its propensity for corrosion. Again, no quantitative analysis is possible by this invention. Another U.S. Pat. No. 4,376,027 discloses a compact, self-contained portable electrolytic testing device for placement against a metal alloy to provide an electronic current through a deposit of color responsive electrolyte to determine the presence of a specific metal. Again, no quantitative analysis is possible by this device.
The inventor's previously issued U.S. Pat. No. 4,799,999, discloses a method for determining the assay of gold alloy between about six to about 14-karat gold utilizing an electrolyte deposited on a sample of precious metal such as to create a wet junction and driving an electric current through the electrolyte to anodize the junction and thereafter terminating the electric current and monitoring the decay in the potential of the sample at the wet junction and comparing the one-time measured potential during the decay period with an empirical table of standards and interpolating and reporting the result. This invention, while capable of reporting accurate results, is limited to the lower end of the scale of gold-containing alloys, namely those in the area of about six to about 14-karat gold. Higher karatage gold alloy does not respond significantly to the method disclosed in said patent, i.e., from 14 to 24-karat gold gives the same result by this method.